In North Carolina, the DSCC reserved airtime starting Sept. 16 and running through Election Day. The amount of money spent will increase each week, from $376,000 the week of Sept. 16, to $1.2 million in the final week before the election.

These reservations can change until shortly before the advertisement's run date.

The DSCC is spending the most funds in the more expensive Charlotte and Raleigh-Durham media markets. Those buys begin Septe. 16. Buys in the Greensboro media market do not begin until Sept. 30, and the DSCC has reserved fewer points in advertisement there.

Outside groups have already begun spending heavily in the highly contested race. Senate Majority PAC, American Crossroads and Americans for Prosperity have spent millions on the race.

The race is rated Tossup by the Rothenberg Political Report/Roll Call.